US3556109A - Method of making a smoking product of oxidized cellulosic materials containing ashing ingredients - Google Patents

Abstract

A smoking product formed of cellulosic material and processed to incorporate ash-forming ingredients by treatment of the cellulosic material with a salt forming composition in which the cation is a heavy metal, preferably calcium, magnesium, barium or strontium, and the anion is an organic acid group, preferably oxalic, pivalic, tannic, glycolic, diglycolic or lactic, preferably with subsequent oxidation of the treated cellulose.

Description

United States Patent lnvemors Theodore S. Briskin;

Geoffrey R. Ward, Beverly Hills, Calif. Appl. No. 745,348 Filed July 17, 1968 Continuation-impart of Ser. No. 595,622, Nov. 21, 1966, Pat. No. 3,447,539, and Ser. No. 674, 994, Oct. 12, 1967. Patented Jan. 19, 1971 Assignee Sutton Research Corporation Los Angeles, Calif. a corporation of Delaware METHOD OF MAKING A SMOKING PRODUCT OF OXIDIZED CELLULOSIC MATERIALS CONTAINING ASI'IING INGREDIENTS 17 Claims, No Drawings US. Cl .Q 131/2, 117/143, 8/1 16.2 Int. Cl ..A24b 15/00, D06m 01/00 Field ofSearch 131/2, 17, 140--l44 Sax (Text) Dangerous Properties of Industrial Materials'- pub. by Reinhold Book Corp. NY. d 1968) p. 987 cited Primary Examiner-Melvin D. Rein Attorney-McDougall, Hersh, Scott & Ladd ABSTRACT: A smoking product formed of cellulosic material and processed to incorporate ash-forming ingredients by treatment of the cellulosic material with a salt forming composition in which the cation is a heavy metal, preferably calcium, magnesium, barium or strontium, and the anion is an organic acid group, preferably oxalic, pivalic, tannic, glycolic, diglycolic or lactic, preferably with subsequent oxidation of the treated cellulose.

METHOD OF MAKING A SMOKINGPRODUCT F OXIDIZED CELLULOSIC MATERIALS CONTAINING ASI-IING INGREDIENTS This is a continuation-in-part of our copending applications Ser. No. 595,622, filed Nov. 21, 1966, and entitled Smoking Products." now U.S. Pat. No. 3,447,539; and Ser. No. 674,994, filed Oct. 12, l967, and entitled Smoking Products and Process for Making Such Products."

As used herein, the term smoking products" is meant to refer to and to include filler material embodied in cigarettes, cigars and for use with pipes and the like, and mixtures thereof with various proportions of tobacco and including cigarette papers and wrappers used in the preparation of such cigars and cigarettes, and it includes cigarettes, cigars and the like products manufactured with such filler materials and Wrap pers.

In the aforementioned copending applications, description is made of the preparation of a smoking product suitable for use in cigarettes, cigars or with pipes wherein the smoking product is prepared of relatively pure cellulosic materials subjected to selective oxidation with liquid nitrogen dioxide to convert preferably more than 90 percent of the methylol groups in the cellulosic molecule to yield a product which can be referred to as an oxycellulose or polyuronic acid. The oxidation reaction product is further processed by removal of liquid nitrogen dioxide by vaporization and preferably by washing the oxidized cellulosic product with water and/or al' cohol and/or acetone or other solvent for removal of solubilized foreign material, including oils, waxes, latices and the like, which contribute undesirably to the taste and aroma when used as a smoking product in accordance with the practice ofthis invention.

As further described in the aforementioned copending applications, the oxidized and cleansed cellulosic derivative is further processed by a reduction reaction with borohydrides of an alkali or alkaline earth metal such as sodium or lithium borohydride for reduction of such nitrogen compounds, quinones, ketones, aldehydes and unsaturates as otherwise have a tendency to impartundesirable aroma and taste as the smoking product is burned. The product before or after reduction can be subjected to additional oxidation with a dilute peroxide solution as a meansfor eliminating further groupings which impart undesirable aroma or taste to the product.

The resulting smoking product is then formulated with mineralizing agents such as oxalates, glycolates, diglycolates, lactates, pivalates ortannates of such metals as calcium, magnesium, lithium, potassium, 'barium or strontium, preferably introduced to form the salt internally in the cellulosic derivative for purposes of providing desired ashing characteristics. Instead of forming the described salts internally in the cellulosic derivative, beneficial characteristics can be achieved by external application of such mineralizing agents. As described, the desired internal introduction is achieved by first wetting the cellulosic derivative with metal cation in dilute solution for absorption into the cellulosic derivative followed by exposure to the acid anion in solution toprecipitate the metal salt in situ in the cellulosic material.

The treated cellulosic derivatives can be further processed to improve the burning, glow and smoking characteristics by formulation to include a potassium salt, such as potassium oxalate or by the addition of rubidium or cesium in the form of compounds thereotin amounts within the range of 0.1 percent to percent by weight but preferably less than 1 percent by weight, as described in the copending application Ser. No. 623,528, filed Mar. I6, 1967, now abandoned, and entitled Smoking Products and Process for their Manufacture. Smoke generators for improving the appearance of the smoke generated by the product can be introduced as by the introduction of dimethyl tartrate of various fatty acids, esters. ethers, and the like and the aroma and pH characteristics can be achieved by the addition of volatilizable alkalyzing material such as ammonium oxalate and the like.

The resulting product is suitable for use as a smoking product alone or in admixture with tobacco to produce a smoking product having good taste, good aroma and good appearance.

As used herein, the term cellulosic material" relates to various forms of cellulose, such as wood pulp, alpha-cellulose, flax, fibrous carbohydrates, seaweed carbohydrates, bamboo filaments, cotton filaments, hemp. straw, refined paper. rice paper, filamentous gums and even plants and plant leaves or weeds and the like fibrous or sheet materials from which noncarbohydrate components have been separated, all of which is hereinafter referred to as cellulosic material.

It is preferred to make use of a purifiied cellulosic material from which various of the sugars, proteins, chlorophylls, flavoncs, colors, lignins, oils, waxes. resins and latices have been removed since these contribute undesirable odors and tastes to thesmoking product.

It has been found that a smoking product should have ash forming ingredients in amounts ranging from I percent to 30 percent by weight of the smoking product and preferably 15 percent to 25 percent by weight of the smoking product, calculated on the basis of ash produced on burning.

It has been found that insufficient ash forming ingredients in the smoking product results in a coalescence or coagulation of the pyrolyzing carbohydrate to form a melt of materials during the smoking process. The result is a coagulative anaerobic pyrolysis which tends to smother the fire to the extent that the cigar or pipe or cigarette soon becomes extinguished. Upon relighting, the smoking product gives a bad taste, at least during the initial puffs, and the smoking product again becomes extinguished after a very short time thereby to constitute a most undesirable and unacceptable product. Furthermore,

this anaerobic pyrolysis produces undesirable muffled bonfire odors.

It is an object of this invention to produce and to provide a method for producing a smoking product of cellulosic material containing ash forming ingredients of a type and concentration to human ash of sufficient coherence and porosity to enable the ash to build up on the end of the smoking product without interfering with or blocking access of air to the burning area thereby to enable the desired burning rate to be maintained; which does not introduce undesirable taste or odor to the smoking product or the product when smoked, in which the ashing components are present in an amount that does not undesirably interfere with the burning rate or pleasure derived from the smoking product, and which gives the desired appearance and aesthetic values as derived from currently used tobacco, and especially to provide a reticulum adequate to absorb molten oxycellulose so that it does not coagulate into an anaerobically pyrolyzing tarry mass.

Attempts have been made to employ inert inorganic substances, such as talc, perlite, calcined alumina, titanium dioxide and the like fillers as mineralizing agents for ashing purposes but these have not proven to be sufficiently successful, when used alone, for various reasonsincluding the inability to .hold the ash and their tendency to coat around the organic material and encourage anaerobic pyrolysis with consequent smothered bonfire odors.

As described in the aforementioned copending parent applications, the desired ashing characteristics are provided in a smoking product formulated of cellulosic material, in accordance with the preferred practice of this invention, by formulation of the cellulosic smokingproduct with calcium or magnesium oxalate. The calcium and magnesium oxalate have greater thermal stability than the oxidized cellulosic material whereby the latter is burned off first during use of the smoking product and the calcium or magnesium oxalate, upon combustion of the oxidized cellulosic material,.breaks down into calcium or magnesium oxides and carbonates which remain in the ash and carbon monoxide and carbon dioxide which go off with the smoke. The ash that remains in porous with sufficient coherence to be sustained on the burned end of a cigar or cigarette until flicked off.

While the invention will be described with reference to the use of calcium oxalate as the mineralizing or ashing component, it will be understood that instead of Calcium oxalate use can be made of equivalent amounts of other salts such as are formed of a cation selected from the group consisting of alkali and alkaline earth metals, and preferably calcium and magnesium, and an anion selected from the group consisting of glycolic acid, diglycolic acid or lactic acid, and preferably oxalic acid, tannic acid or pivalic acid. The preferred ashing component is calcium oxalate and/or magnesium oxalate.

lmprovement in the characteristics of the ash left by the burned smoking product is achieved when calcium oxalate is present in uniform distribution in the cellulosic smoking product in an amount as little as 1 percent by weight but it is preferred to make use of cellulosic material containing calcium oxalate and/or magnesium oxalate sufficient to give an ash of percent to percent by weight, calculated on the basis of calcium carbonate ash (40 parts by weight of calcium oxalate being approximately equivalent to 30 parts by weight of calcium carbonate). When more than 30 percent by weight ash level is present in the cellulosic material, the dilution of the cellulosic material becomes excessive so that the desired burning or smoking characteristics are difficult to achieve and it is also difficult to maintain the desired burning rate, and smothered odors begin to appear.

In our copending application Ser. No. 745,370 filed concurrently herewith and entitled "Smoking Product of Cellulosic 1 Material including Ashing and Mineralizing Ingredients and Method," description is made of a process wherein calcium oxalate or the like ashing ingredients are formed internally in -an oxidized cellulosic material by first exposing the oxidized cellulosic material to a solution containing the calcium ion whereby calcium can react to form a corresponding calcium polyuronate and then exposing the oxidized cellulosic material to a solution containing the anion whereby the more insoluble, more thermally stable calcium oxalate is formed in situ in the oxidized cellulosic material. Since such ingredients are preferably employed in dilute solutions, the amount of calcium oxalate retained in the oxidized cellulosic material will in some cases be insufficient from a single treatment. Thus the treating cycle can be repeated a number of times until the desired concentration of ash forming ingredients is embodied within the cellulosic material.

Conventional fillers of the types described can be used to reduce the concentration of calcium oxalate required but it is desirable to have at least 5 percent by weight calcium oxalate and/or magnesium oxalate and the like mineralizing salts in the oxidized cellulosic smoking product.

The aforementioned copending application is addressed to the procedure wherein the cellulosic material is in an oxidized state whereby polyuronic acids are available for receiving calcium ions internally in salt formation to enable internal ashing ingredients to be formed upon subsequent addition of oxalic or the like acid.

This invention will be addressed to the introduction of the ashing ingredients into the cellulosic material in the absence of oxidation of the cellulosic material but preferably with oxidation of the cellulosic material after incorporation of the ashing or mineralizing agents.

As in the aforementioned copending application, it is still more desirable to disperse the calcium oxalate and/or magnesium oxalate or others of the mineralizing agents internally within the cellulosic material, although limited benefit can be obtained by the incorporation of the calcium and/or magnesium oxalate and the like on the outside of the cellulosic fibers or interstitially between the fibers.

The described oxalates are insoluble and the problem there fore arises of techniques whereby such normally insoluble mineralizing agents might be embodied into the cellulosic material other than by mere physical entrainment. We have found that calcium and/or magnesium oxalate and the like mineralizing agents can be introduced into the cellulosic material by taking advantage of the short lapse oftime that is experienced after the solutions containing the anion and cation are brought together and until precipitation of the insoluble salt takes place. it appears that calcium oxalate remains in the dissolved state or soluble state in aqueous medium for a sufficient length of time to enable substantial impregnation or penetration of the cellulosic material before the calcium oxalate is converted to its insoluble form and precipitates. lt is believed that this delay results from the fact that the calcium ions are initially sufficiently hydrated to form an insoluble hydrated calcium oxalate which becomes insoluble as it loses water of hydration. The time lapse is somewhat proportional to temperature so that it is preferred to work at lower temperatures to provide a longer time before precipitation takes place. This same phenomenon is experienced with magnesium oxalate where the aging effect seems to be even more pronounced.

In the practice of this invention, separate solutions are prepared, one ofwhich is formulated to contain the calcium or magnesium cation in a concentration in aqueous medium within the range of 1 percent to 15 percent by weight while the other solution is formulated to contain the acid anion, such as oxalic acid or an ammonium or sodium salt capable of providing the desired anion, in an amount within the range of l percent to 15 percent by weight. Treatment to incorporate the calcium oxalate and/or magnesium oxalate can be carried out at a temperature up to 40 C but it is preferred to make use of a temperature below ambient temperature down to the freezing point for the solution (about -3 C) in order to provide a greater margin of time for penetration of the cellulosic material before insolubilization of the oxalate. For this purpose, the cellulosic material should be dry so that it will rapidly absorb the treating solution and the two solutions of anion and cation should be combined almost immediately prior to impregnation or applied directly to the .cellulosic material substantially simultaneously in equivalent amounts for impregnation.

Application can be made by spraying the mixture onto the dry cellulosic material with proper agitation for uniform distribution. Instead. the mixture of solutions can be added to the cellulosic material in a suitable mixer or homogenizer for uniform distribution. Still further, the mixture of solutions or the separate solutions can be applied directly onto a thin continuous web of paper formed of a purified cellulose or of alpha-cellulose in a substantially continuous operation.

When such techniques are employed for mineralizing the cellulosic material, the aqueous solutions can be applied in amounts to provide the desired concentration of calcium oxalate. After application, a sufficient aging period should be allowed to complete the insolubilization reaction to form the calcium oxalate.

With either technique for incorporation of the mineralizing agent in the amounts described, excess materials can be removed by rinsing the treated cellulosic material with water after which the treated product can be dried.

in the event that the treated cellulosic material is to be employed as a smoking product without oxidation of the cellubarium or strontium or other alkaline earth metals. As the tannic, glycolic, diglycolic or lactic acid groups in correspond ing amounts, if due allowance is made for the aqueous solubilivty of such derivatives.

By way of modification, it has been found that a smoking product having the desired ashing and smoking characteristics ever,-it is undesirable to make use ofa smoking product containing less than 5 percent by weight of the calcium oxalate or the like mineralizi ng agents of the type described. Such inorganic dilutentsor agents can be admixed dry before or after treatment of the cellulosic material and blended to achieve uniform distribution with additions being made in amounts to provide a total ashingflcomponent which, when coupled with the mineralizing agent, does not exceed 30 percent be weight of the smoking product.

Having described the basic concepts of this invention, examples will now be given by way of illustration, but not by way of limitation, of the invention.

EXAMPLE 1 A 6 percent water solution of calcium acetate is provided in one container and a 6 percent water solution of oxalic acid is provided in another. The two solutions are rapidly mixed one with the other in a container and immediately sprayed with mixing onto a purified cellulose pulp in amounts calculated to wet the material with its equal weight of liquid. Application is made by spraying while the materials are maintained at a tem perature within the range of 0 to C to provide a cellulosic material in which calcium oxalate is formed in situ by reaction between the dissolved calcium acetate and oxalic acid within the fiber. After aging the material for an hour to permit the process to reach completion, the treated cellulosic material is thoroughly washed with water to remove the water solubles, including excess acid, and the resulting product is dried. The ash level will be about 2 percentto 4percent by weight and the ash level can be increased to the desired concentration by repeating the treatments a number of times.

EXAMPLE 2 The process of Example 1 is repeated except that a shredded paper formed of purified cellulosic material is used instead of cellulose pulp. After r'epeated application of the solutions to incorporate percent to 25 percent by weight of calcium oxalate, 0.1 percent by weight oxalic acid is reintroducedfrom aqueous solution with mixing into the dried cellulosic material for reaction to take ,up residual heavy metal ions present in the treated cellulosic material or subsequently released therein.

EXAMPLE 3 The procedure is the same as that of Example 1 except that use is made of a 3 percent by weight solution of magnesium acetate and a 3 percent by weight solution of oxalic acid with the-solutions sprayed simultaneously without mixing onto a thin web of purified alpha-cellulosic paper in a room maintained at a temperature of about 5 to 10 C and in amounts thoroughly to wet the paper.

Several applications are made with intermittent drying until a magnesium oxalate content is obtained of the order of 25 percent by weight. The dried web is then rinsed with a copious amount of water to remove water solubles and the web is thereafter again dried.

EXAMPLE 4 The procedure is the same as in Examples] and 3 except that application'ismade to cellulosic material in an amount to provide for a concentration of 10 percent by weight calcium oxalate. Application is made to a paper web formed of alphacellulose containing 15 percent to 20 percent by weight filler such as calcium carbonate, talc, silica, perlite, alumina or mixtures thereof to give a total ashing component within the range of 25 percent to 30 percent by weight.

in Examples 1 to 4, the calcium acetate can be replaced with corresponding amounts of magnesium acetate, barium acetate or strontium acetate. Alternatively, instead of the acetates, the alkaline earth metal salts of lactic, glycolic or glucuronic acids can be used. The oxalic acid can be replaced with corresponding amounts of tannic acid. When magnesium is used the precipitation reaction is somewhat slower so that a longer aging period is required or the material can be dried after spraying to complete the reaction before water washing. Alternatively, water soluble ash generators such as calcium or magnesium salts of glycolic, diglycolic, lactic or pivalic acid can be applied by direct spraying if no subsequent aqueous rinsings are employed since such glycolic, diglycolic, lactic or pivalic acid salts are relatively soluble in water.

The product of Examples 1 to 4 will give improved smoking characteristics by comparison with the cellulosic materials prior to treatment.

Since the calcium oxalate and other mrineralizing agents embodied within the cellulosic material do not interfere with sub sequent processing by way of oxidation and the like, the cellulosic materials, mineralized in accordance with the practice of this invention, are preferably further processed to improve their smoking characteristics, as described in the aforementioned copending application, to oxidize the cellulosic material, subjecting the oxidized cellulosic material to selective reduction reaction with borohydride as described in the aforementioned copending applications and/or by modification of the treating material to incorporate various agents, such as agents for controlling glow and burning rate by the addition of potassium, rubidium or cesium salts, as described in the aforementioned copending applications, andfor by the addition of agents for providing neutralization of the smoke, such as ammonium or amine salts, and/or the incorporation of coloring and the like agents as described in the aforementioned copending applications.

More specifically, as described in our copending application Ser. No. 745,221 filed concurrently herewith and entitled A Smoking Product and Method of Preparation, description is made of the oxidation of a cellulosic material by suspension in liquid nitrogen dioxide in the ratio of l part by weight cellulosic material to 5 to 1000 parts by weight liquid nitrogen dioxide and preferably 1 part by weight cellulosic material to 25 to 50 parts by weight of liquid nitrogen dioxide. The reaction therein is carried out at a temperature within the range of 15 to 65 C and at an autogenous pressure when the reaction temperature exceeds 21 C (the boiling point of nitrogen dioxide, N204).

In our copending application Ser. No. 745,135, new U.S. Pat. No. 3,49 l ,766 filed concurrently herewith and entitled Preparation of Smoking Product of Cellulose Derivatives and Process," description is made of the selective oxidation of cellulosic material wherein the oxidation reaction, including reaction rate and the amount of conversion, is materially im proved by formulation of the oxidation reaction medium to contain up to 8 percent by weight of water in the liquid nitrogen dioxide system and by carrying out the reaction at temperatures above 15 C and preferably within the range of 20 to 45 C, depending somewhat upon the amount of moisture present in the reaction medium, whereby the reaction medium is rendered relatively nonelectrically conductive so that the presence of water in the reaction medium will not result in attack or degradation of the cellulosic material to be oxidized and wherein the formulation to include aqueous medium in the reaction of liquid nitrogen dioxide operates also to adjust the specific gravity of the reaction medium in the direction towards the specific gravity of the cellulosic material whereby suspension of the cellulosic material in the reaction medium is easier to achieve and maintain. The result is a more rapid and uniform oxidation reaction of the cellulosic material to produce a better product at a more rapid rate.

-ln our copending application Ser. No. 745,132, now US. Pat. No. 3,498,751 filed concurrently herewith and entitled Method for Preparation of Smoking Product with Selective Reduction following Selective Oxidation," description is made of the treatment of the oxidized cellulosic material to effect reduction of any nitro groups as well as quinone, ketone and aldehyde groups present in the oxidized cellulosic material or impurities entrained therewith, by treatment with an alkali metal or alkaline earth metal borohydride or nascent hydrogen at a pH within the range of 3 to 7 and at a temperature within the range of to 30 C, with the oxidized cellulosic material admixed with one to 1,000 times its weight of an aqueous solution of the soluble borohydride present in a concentration within the range of 0.05 percent to percent by weight.

Beneficial ashing characteristics of limited utility can also be achieved by the external application of the described mineralizing agents as by the direct introduction of calcium oxalate and/or magnesium oxalate or others of the described mineralizing agents for suspension in aqueous medium applied for uniform distribution with the cellulosic material. Instead, such mineralizing agents may be blended in the desired amounts into the cellulosic material by admixture in dry powdered form for uniform distribution throughout the smoked product but it is the preferred concept of this invention to incorporate such mineralizing agents internally in the cellulosic smoking product.

An improved cellulosic smoking product can be prepared at low cost and high yield, with a minimum number of processing steps, by the incorporation of a mineralizing or ashing ingredient in the manner described above, as a filler for the fibers or paper formed thereof, in an amount within the desired range (ash basis) of 10 percent to 30 percent by weight of the fiber and preferably percent to 25 percent by weight and thereafter subjecting the cellulosic material to nitrogen dioxide oxidation in the manners previously described, preferably followed by rinsing the oxidized cellulosic material with a dilute aqueous or alcoholic solution of an acid such as pivalic,-tannic, glycolic, diglycolic, lactic and preferably oxalic acid, or mixtures thereof, to form the cori responding salt with heavy metal ions that might remain or be subsequently released in the filled oxidized cellulose.

As described, the ashing ingredient can be incorporated into the cellulosic material by the technique previously described or, as in the preferred practice of this-modification of the invention, the ashing ingredient may be incorporated directly as calcium or magnesium oxalate or the like suspended in the slurry of the cellulosic fibers supplied as a furnish in paper making. It is preferred, in the practice of this invention, to make use of calcium oxalate and magnesium oxalate and preferably a mixture of calcium and magnesium oxalate in the ratio of 1 part by weight magnesium oxalate to l to 5 parts by weight calcium oxalate as the ashing ingredient incorporated directly into the fibrous system instead of or in addition to the conventional fillers.

The following will illustrate the practice of this concept of the invention.

EXAMPLE 5 oxalate uniformly distributed throughout the fiber system.

The paper is cut into shreds and suspended in 100 times it weight of liquid nitrogen dioxide and maintained at C for fsix to eight days until at least 90 percent of the methylol groups of the cellulosic molecule have been converted. The oxidized cellulosic material is driedand heated to remove nitrogen dioxide and other volatiles and then the dried oxidized cellulosic material is rinsed with copious amounts of 0.3 percent by weight solution of oxalic acid in deionized water. The oxidized cellulosic material, after drying, finds use directly as a smoking product having improved aroma and taste.

EXAMPLE 6 The procedure of lixample 5 is followed except that instead of introducing the calcium and magnesium oxalate into the pulp slurry from which the paper is formed, the calcium and magnesium oxalates are introduced by immersion of an already formed paper of cellulosic material into a 1 percent to 5 percent by weight suspension of calcium and magnesium oxalate in aqueous medium to impregnate the-fibrous mass. One or more passes can be made until the paper acquires 20 percent to 30 percent by weight of calcium and magnesium oxalate.

Thereafter the paper can be treated as in the previous example except that the liquid nitrogen dioxide is formulated to contain about 1.5 percent by weight water and the reaction is carried out at a temperature of 35 C.

The oxidized paper. without and preferably with addition to incorporate about 0.1 percent to 0.5 percent by weight oxalic acid, uniformly distributed throughout the fibrous mass, can be used as a smoking product.

It will be understood that changes may be made in the details of formulation and operation without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. In the preparation ofa smoking product of oxidized cellulosic material the steps of introducing an ashing component in the form of a salt of a cation selected from the group consisting of calcium, magnesium, barium and strontium and an anion selected from the group consisting of oxalic, pivalic, glycolic, diglycolic and lactic acids in uniform distribution throughout cellulosic material in an amount within the range of 1 percent to 30 percent by weight of the cellulosic material, in which the ashing ingredient is introduced by wetting the cellulosic material with the salt forming components in a solubilized state in aqueous medium and then oxidizing the cellulosic material with liquid nitrogen dioxide selectively to oxidize the methylol groups on the C position of the cellulosic molecule by an amount to convert at least percent of the C methylol groups to carboxyl groups, separating the oxidized cellulose from the liquid oxidizing medium after oxidation has been completed and drying the oxidized cellulosic material.

2. The process as claimed in claim 1 in which the ashing component is selected from the group consisting of calcium oxalate and magnesium oxalate and mixtures thereof.

3. The process as claimed in claim 1 comprising the steps of providing one aqueous solution containing the cation and a second aqueous solution containing the anion and substantially simultaneously wetting the cellulosic material with the solutions.

4. The process as claimed in claim 3 in which the solutions are admixed immediately prior to wetting the cellulosic material.

5. The process as claimed in claim 3 in which the solutions are separately applied substantially simultaneously onto the cellulosic material.

6. The process as claimed in claim 1 in which the cellulosic material is immersed in liquid nitrogen dioxide and in which the oxidation reaction is carried out at a temperature within the range of 15 to 65 C.

7. The process as claimed in claim 1 in which oxygen containing gas is bubbled through the liquid nitrogen dioxide during the oxidation reaction.

8 The process as claimed in claim 1 in which the liquid nitrogen dioxide contains 0.5 percent to 5 percent by weight water and in which the oxidation reaction is carried out at a temperature at which the oxidizing medium is not electrically conductive.

9. The process as claimed in claim 8 in which the liquid oxidizing medium is maintained at a temperature within the range of 20 to 65 C.

10. The process as claimed in claim 1 which includes the step of rinsing the oxidized cellulosic material with anhydrous liquid nitrogen dioxide after separationof the liquid oxidizing medium and before drying.

11. The process as claimed in claim 1 which includes the step of rinsing the oxidized cellulosic material with a dilute aqueous solution of an acid selected from the group consisting of oxalic, pivalic, glycolic, diglycolic and lactic acids.

12. The process as claimed in claim 1 in which the oxidized cellulosic material is rinsed with a dilute solution of oxalic acid in an amount to leave up to 0.5 percent by weight free acid in the dried oxidized cellulosic material.

13. The process as claimed in claim 1 which includes the step of subjecting the oxidized cellulosic material to a mild reduction reaction with a medium selected from the group consisting of hydrogen and a borohydride.

14. The process as claimed in claim 13 in which the borohydride is selected from the group consisting of an alkali metal borohydride and an alkaline earth metal borohydride.

15. The process as claimed in claim 1 in which the ashing ingredient is introduced as a salt into the cellulosic material and in which the salt is formed of a cation selected from the group consisting of an alkaline earth metal and an anion selected from the group consisting of oxalic acid. pivalic acid, glycolic acid and lactic acid.

16. The process as claimed in claim 15 which includes the step of reintroducing oxalic acid into the dried oxidized cellulosic material in an amount within the range of 0.1 percent to 0.5 percent by weight.

17. The process as claimed in claim 1 in which the salt is present in an amount of at least 5' percent by weight of the cellulosic material while the remainder is a filler selected from the group consisting of talc, perlite, calcium carbonate, alumina and silica.

Claims (16)

1. 2. The process as claimed in claim 1 in which the ashing component is selected from the group consisting of calcium oxalate and magnesium oxalate and mixtures thereof.
2. 3. The process as claimed in claim 1 comprising the steps of providing one aqueous solution containing the cation and a second aqueous solution containing the anion and substantially simultaneously wetting the cellulosic material with the solutions.
3. 4. The process as claimed in claim 3 in which the solutions are admixed immediately prior to wetting the cellulosic material.
4. 5. The process as claimed in claim 3 in which the solutions are separately applied substantially simultaneously onto the cellulosic material.
5. 6. The process as claimed in claim 1 in which the cellulosic material is immersed in liquid nitrogen dioxide and in which the oxidation reaction is carried out at a temperature within the range of 15* to 65* C.
6. 7. The process as claimed in claim 1 in which oxygen containing gas is bubbled through the liquid nitrogen dioxide during the oxidation reaction.
7. 8. The process as claimed in claim 1 in which the liquid nitrogen dioxide contains 0.5 percent to 5 percent by weight water and in which the oxidation reaction is carried out at a temperature at which the oxidizing medium is not electrically conductive.
8. 9. The process as claimed in claim 8 in which the liquid oxidizing medium is maintained at a temperature within the range of 20* to 65* C.
9. 10. The process as claimed in claim 1 which includes the step of rinsing the oxidized cellulosic material with anhydrous liquid nitrogen dioxide after separation of the liquid oxidizing medium and before drying.
10. 11. The process as claimed in claim 1 which includes the step of rinsing the oxidized cellulosic material with a dilute aqueous solution of an acid selected from the group consisting of oxalic, pivalic, glycolic, diglycolic and lactic acids.
11. 12. The process as claimed in claim 1 in which the oxidized cellulosic material is rinsed with a dilute solutiOn of oxalic acid in an amount to leave up to 0.5 percent by weight free acid in the dried oxidized cellulosic material.
12. 13. The process as claimed in claim 1 which includes the step of subjecting the oxidized cellulosic material to a mild reduction reaction with a medium selected from the group consisting of hydrogen and a borohydride.
13. 14. The process as claimed in claim 13 in which the borohydride is selected from the group consisting of an alkali metal borohydride and an alkaline earth metal borohydride.
14. 15. The process as claimed in claim 1 in which the ashing ingredient is introduced as a salt into the cellulosic material and in which the salt is formed of a cation selected from the group consisting of an alkaline earth metal and an anion selected from the group consisting of oxalic acid, pivalic acid, glycolic acid and lactic acid.
15. 16. The process as claimed in claim 15 which includes the step of reintroducing oxalic acid into the dried oxidized cellulosic material in an amount within the range of 0.1 percent to 0.5 percent by weight.
16. 17. The process as claimed in claim 1 in which the salt is present in an amount of at least 5 percent by weight of the cellulosic material while the remainder is a filler selected from the group consisting of talc, perlite, calcium carbonate, alumina and silica.